Question

You buy a magnifying glass at the store. The lens in the magnifying glass is a double convex lens, a lens with two convex curved surfaces. You determine the focal length of the lens is +25 cm. Of both sides of the lens have about the same radius of curvature and the lens is made of a glass with index of refraction 1.6, what is the radius of the glass surfaces?

Answer 1

30 cm

Step-by-step explanation:

f = Focal length = 25 cm

R = Radius of curvature (both sides are equal)

`\mu` = Refractive index of lens = 1.6

The lens maker formula is given by

`(1)/(f)=(\mu-1)((1)/(R_1)-(1)/(R_2))\\\Rightarrow (1)/(f)=(\mu-1)((1)/(R)-(1)/(-R))` minus sign because it is on the other side

`\\\Rightarrow (1)/(f)=(\mu-1)(2)/(R)\\\Rightarrow R=2(\mu-1)f\\\Rightarrow R=2(1.6-1)* 25\\\Rightarrow R=30\ cm`

The radius of curvature of the glass surface is 30 cm